This research will study the molecular mechanism of peptide chain initiation in animal cells and the roles of different factors in regulation of protein synthesis under different physiological conditions, which include mitogen stimulation and viral infection. The first step in peptide chain initiation is the formation of a ternary complex between the eukaryotic peptide chain initiation factor 2 (eIF-2), Met-tRNAf and GTP,MET-tRNA.f eIF-2-GTP. The next step is the transfer of Met-tRNAf. 40S mRNA complex. An important regulatory mechanism involves one or more eIF-2 kinases and an eIF-2 kinase inhibitor (a 67 kDa polypeptide - p67). eIF-2 kinases phosphorylate eIF-2 and thus inhibit protein synthesis and the increased availability of p67 renders eIF-2 resistant to eIF-2 kinase phosphorylation and so promotes protein synthesis in the presence of eIF-2 kinases. Objectives of the research are: (1) Studies of the characteristics and factor requirements for ternary and Met-tRNAf. 40S mRNA complex formation. Endeavors will be made to extensively purify different protein factors and analyze their roles and requirements in ternary and Met-tRNAf. 40smRNA complex formation. Also, Drs. Hershey and Merrick agreed to supply peptide chain initiation factors purified in their laboratories. The investigators will also compare the factor preparation from all three laboratories (Gupta, Hershey, Merrick) and arrive at a mutually agreeable definition regarding the characteristics and requirements for these factors in ternary and Met-tRNAf. 40S mRNA complex formation. (2) Studies of the regulation of protein synthesis initiation. Emphasis will be given to the studies of the roles of p67 and eIF-2 kinases in the regulatory process. Efforts will be made to determine qualitative and quantitative changes in p67, eIF-2 kinases and other factor activities during mitogen stimulation, as well as during polio viral infection. These changes will then be related to the protein synthesis activities of the cells.